these days a lot of people are choosing the ADN first since it is an employable degree (while 2 years taking pre-nursing is not) and then go on to their BSN.
Instead of a 4-year program at the same school you could get an RN at a community college (an ADN degree) and then go to one of the RN->BSN programs. Look for a good NCLEX pass rate at the CC. I know nurses that have done this, RN->BSN programs tend to be easier to get into. See http://www.rn.ca.gov/education/rntobsn.shtml for a list. Many are part-time and/or online, but some are campus based. Fullerton, for example, offers both online and on-campus and says
You are never going to find a CA college that says “sure, we have room for all the students who have taken the pre-nursing curriculum at a 4-year college, ours or somewhere else.”
If you go the CC->BSN path you are a RN and are highly likely to get a BSN if you continue, the downside is the college experience is not quite the same as the 4-year path.
Lastly, if you don’t already have experience thru paid or volunteer work with patient care, forget everything I said above. What I’m talking about is for people that already know as sure as someone that is 18 can know that nursing is right for them, not someone exploring their options still.